1) Field of the Invention
The present invention relates to an apparatus providing a communication service guaranteeing a communication quality in an arbitrary time zone by a reservation in a network, preferably in a label switching network. Particularly, the present invention relates to a network controlling apparatus and a path controlling method in the network controlling apparatus suited to be used when a communication service guaranteeing a communication quality in an arbitrary time zone by a reservation is provided in a network employing MPLS (Multiprotocol Label Switching).
2) Description of the Related Art
In recent years, research is carried out to provide a bandwidth guaranteed service guaranteeing a communication quality in an arbitrary time zone by a reservation. The bandwidth guaranteed service is a service in which when a user requests a network to provide a communication guaranteeing a bandwidth, the network secures the bandwidth by a reservation. Whereby, the user can get a guarantee of the communication quality in the secured bandwidth and accept the communication service. Particularly, when an MPLS network provider provides this bandwidth guaranteed service, there is a demand for efficient use of the network resource.
In the MPLS network, a route connecting two edges nodes, which are boundary nodes with external networks, is set as a path identified as an LSP (Label Switched Path), label information differing from header information in a packet such as an IP packet is attached to a packet, the packet is transferred with the label through the path, whereby the packet can be transferred at high speed. Use of the path enables the packet to be transferred through an explicit route. Meanwhile, in relation with the label switching in the MPLS network, there is a technique described in patent document 1 below, for example.
In order to practically secure a bandwidth in the MPLS network and make a communication along a secured route, it is necessary that not the user but the network (network provider) manages the state of use of links configuring the network, sets a path on a route along which the necessary bandwidth can be secured, and accommodates a flow to be guaranteed in the path. For the purpose of guaranteeing the communication quality and using efficiently the network resource at the same time in such the MPLS network, it is necessary to manage the communication quality in each set path in the whole MPLS network.
As an apparatus making a known bandwidth reservation, there is a system of making a bandwidth reservation in, for example, an ATM (Asynchronous Transfer Mode) exchange (refer to patent document 2). In this system, only a bandwidth of a link connected to the ATM exchange is reserved in response to a request, thus a reservation along a route in the whole network is impossible. Namely, this system cannot manage the communication quality of each path being as a unit.
Patent document 3 below shows a technique, wherein a television conference reservation is accepted by a conference reservation server, a communication route satisfying the network resource reservation request for the television conference is determined on the IP (Internet Protocol) network to make a resource reservation, whereby the television conference reservation is accepted.
As a technique aimed to accept a reservation and secure a bandwidth in response to each request, there is a technique with regard to a line reservation apparatus and a reservation accepting apparatus described in patent document 4. In the technique described in patent document 4, it is determined whether or not a reservation can be accepted on the basis of the state of occurrence of reservations, the state of use of the network resource and the possibility of acceptance of the reservation in relation with time in the network.
The techniques described in the patent documents 3 and 4 do not assume a network in which a path for communication is set between two network apparatuses in the network. The techniques thus do not give consideration to what route the path is set along according to contents of the reservation, whether or not a plurality of reservations are accommodated in the same path, and whether or not different paths are set for the plural reservations, for the purpose of efficient use of the network resources.
As methods of securing a bandwidth responsive to a quality guarantee request in the MPLS network: (1) a first method is of beforehand setting paths among all edge nodes at which quality guarantee can be requested, accommodating a request in the set path when the request is accepted, and managing the remaining bandwidths of the links; (2) a second method is of making a route calculation each time a request occurs, and setting a path in which the bandwidth is secured; and (3) a third method is of making a route calculation to set a path when a request occurs, securing a bandwidth greater than the requested bandwidth, and generating an intensive path which can accommodate requests that may occur thereafter in the same section.
Patent Document 1: Japanese Patent Laid Open (Kokai) Publication No. 2002-300194
Patent Document 2: Japanese Patent Laid Open (Kokai) Publication No. HEI 6-30021
Patent Document 3: Japanese Patent Laid Open (Kokai) Publication No. 2003-309832
Patent Document 4: Japanese Patent Laid Open (Kokai) Publication No. HEI 8-125654
In a network providing a service of accepting a reservation of the bandwidth guaranteed service and guaranteeing a bandwidth in an arbitrary time period, there is desired a method of efficiently assigning the network resource according to the state of occurrence of the requests since the requested bandwidths, sections, length of time, and the amount of occurring requests are changed with time, thereby satisfying the requests, when the bandwidth is secured in response to a quality guarantee request in the above MPLS network.
With respect to this point, the first method [1] above described poses a problem that it uses only a predetermined path, thus cannot change the route even when the state of use of the links changes with time, which leads to a trouble when effective use of the network resource is aimed. The method also fails improvement of the loss probability.
The second method [2] can appropriately assign the network resource (for example, bandwidth) because the route calculation and setting are performed for each request, but lacks the scalability because the processing overhead increases.
The third method [3] can decrease the processing overhead because a bandwidth greater than the requested bandwidth is secured, but wastefully secures the resource because bandwidths not to be used is also secured.